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This scientific independent research is provided by Aisle7 and is for informational use only. GNC provides this information as a service but does not endorse it. Likewise, Aisle7 does not recommend or endorse any specific products.

For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.

Our proprietary "Star-Rating" system was developed to help you easily understand the amount of scientific support behind each supplement in relation to a specific health condition. While there is no way to predict whether a vitamin, mineral, or herb will successfully treat or prevent associated health conditions, our unique ratings tell you how well these supplements are understood by some in the medical community, and whether studies have found them to be effective for other people.

For over a decade, our team has combed through thousands of research articles published in reputable journals. To help you make educated decisions, and to better understand controversial or confusing supplements, our medical experts have digested the science into these three easy-to-follow ratings. We hope this provides you with a helpful resource to make informed decisions towards your health and well-being.

Supplement

Amount

Why

Creatine Monohydrate(Non-Weight Bearing Endurance Exercise)

15 to 20 grams daily for five or six days

[3 stars]

Taking this supplement for five or six days may improve performance of high-intensity, short-duration exercise (like sprinting) or sports with alternating low- and high-intensity efforts.

2 grams of powdered root daily or 200 to 400 mg daily of an herbal extract standardized for 4% ginsenosides

[2 stars]

Some early studies suggested there might be benefits of using Asian ginseng to improve athletic performance. One study reported increased pectoral and quadricep muscle strength in non-exercising men and women after supplementing with the herb.

Casein protein is more slowly digested than other animal proteins, resulting in a slower, prolonged rise in blood levels of amino acids, so some speculate that it may better support protein synthesis by the body compared with proteins like whey protein that are more rapidly digested.

135 to 225 mg per pound of body weight dissolved in two cups of fluid and taken at least one hour before exercise

[2 stars]

Taking sodium citrate may neutralize the acids produced during exercise that may interfere with energy production or muscle contraction. Some studies have found that sodium citrate typically improves short- to intermediate-duration exercise performance.

Athletes participating in several hours of exercise, especially in hot, humid conditions, should use sodium-containing fluids to reduce the risk of performance-diminishing and possibly dangerous declines in blood sodium levels.

It has been speculated that AAKG may increase production of nitric oxide, a substance known to enhance blood flow. In one study, AAKG improved measures of strength and short-term power performance in weight lifters.

200 mg of an herbal extract, standardized to contain 3% rosavin plus 1% salidroside, taken one hour before endurance exercise

[2 stars]

In a double-blind trial, healthy volunteers who received an extract of the herb Rhodiola rosea one hour before an endurance-exercise test saw significantly increased endurance, as measured by the time it took to become exhausted.

In one study, elderly men participating in a strength training program who took a supplement containing protein (part of which was soy protein) immediately following exercise saw significant gains in muscle growth and lean body mass.

Antioxidants, including vitamin C, neutralize exercise-related free radicals before they can damage the body, so antioxidants may aid in exercise recovery. Especially in cases of vitamin C deficiency, supplementing with the vitamin may improve exercise performance.

Antioxidants, including vitamin E, neutralize exercise-related free radicals before they can damage the body, so antioxidants may aid in exercise recovery. Vitamin E has been shown to benefit exercise performance at high altitudes.

20 grams daily up to 1.2 grams of per 2.2 of pounds body weight per day

[2 stars]

Animal studies suggest that whey protein can increase gains in lean body mass resulting from exercise. One study found that people taking whey protein improved their performance on a test of short-term intense cycling exercise.

Asian ginseng has been associated with improved athletic performance, though findings have been inconsistent. Its cousin, American ginseng, was found ineffective at improving endurance exercise performance in untrained people after one week. It is possible that different amounts and durations might affect results.

At very high intakes, the amino acid arginine has increased growth hormone levels, which stimulate muscle growth. Trials combining weight training with arginine and ornithine showed decreases in body fat and increases in total strength and lean body mass.

Beta-sitosterol, found in many plants, has been shown in one trial to improve immune function in marathon runners when combined with B-sitosterol glucoside. This implies that beta-sitosterol might reduce infections in athletes who engage in intensive exercise.

Gamma oryzanol is a mixture of sterols and ferulic acid esters. One trial using ferulic acid in trained weight lifters found significantly more weight gain and increased strength compared with placebo.

HMB, a breakdown product of an essential branched-chain amino acid, has a role in protein synthesis and might, therefore, improve muscle growth and overall body composition. Research suggests it might be effective only when combined with an exercise program in people who are not already highly trained athletes.

L-carnitine has been popular as a potential aid in improving athletic performance because of its role in converting fat to energy. Some studies have found that it improves certain measures of muscle physiology.

Magnesium deficiency can reduce exercise performance and contribute to muscle cramps. Studies suggest that taking magnesium might improve performance, although possibly only for those who are deficient or who are not highly trained athletes.

Medium-chain triglycerides contain a class of fatty acids that are more rapidly absorbed and burned as energy than other fats. For this reason, athletes have been interested in their use, especially during prolonged endurance exercise.

The developers of methoxyisoflavone, a member of the flavonoid family, claim that it builds bone and muscle without the side effects seen with hormones. One trial found that athletes who took it reduced their body fat more significantly than those taking placebo.

Ornithine alpha-ketoglutarate (OKG) is believed to facilitate muscle growth by enhancing the body's release of anabolic hormones, but this is based on effects seen in hospitalized and elderly people, not published research.

Ribose is a type of sugar used by the body to make the energy-containing substance adenosine triphosphate (ATP), which gets depleted during intense exercise. Reports have suggested that taking ribose might increase power during short, intense bouts of exercise.

Tribulus terrestris extracts have been reported in preliminary studies to affect anabolic hormones in men, though a double-blind trial found no effect on body composition or strength performance from an eight-week strength training program.

B-complex vitamins are needed to produce energy from carbohydrates. Exercisers may have slightly increased requirements for some of the B vitamins, including vitamins B2, B6, and B5, athletic performance can suffer if these slightly increased needs are not met.

Exercise depletes zinc, and severe zinc deficiency can compromise muscle function. One trial found that zinc improved muscle strength, and another study of athletes with low zinc levels found that zinc improved red blood cell flexibility during exercise, which could benefit blood flow to the muscles.

About This Condition

Aside from training, nutrition may be the most important influence on athletic performance.1 However, in seeking a competitive edge, athletes are often susceptible to fad diets or
supplements that have not been scientifically validated. Nevertheless, there is much useful research to guide
the exerciser toward optimum health and performance.

1. American Dietetic Association. Position of the American Dietetic Association and the Canadian Dietetic Association: Nutrition for physical fitness and athletic performance for adults. J Am Diet Assoc 1993;93:691?6.

The information presented by Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2017.